Magnetic bobbin



Dec. 31, 1929. H, H, WERMINE 1,742,018

MAGNETIC BOBBIN Filed June 21. 192e 2 sheets-sheetv 1 Dec. 3l, 1929. H, H, WERMINE I 1,742,018

MAGNETIC BOBBIN Filed June 21, 1928 2 Sheets-Sheet 2 y l I @Z Patented Dec. 31, 1929 iJlal'rErJl STATES "PATENT *ol-FICE HUGO H. WERIMINE, OF VILLA PARK, ILLINOIS, ASSIGNOR TO BELDEN MANFACTUR- ING COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS MAGNETIC BOBBIN Application nled June 21,

The invention relates to improvements in magnetic bobbin and its principal ob] ects are to provide a combined magnetic core and bobbin upon which the electrical Winding may be directly ,wound without the use of auxiliary supports; to provide a windingfhermetically sealed by an enveloping material which will not deteriorate with age or under varying climatic conditions; to provide a coil conn struction having improved copper efficiency, that is to say, of low resistance with high number of turns for a given winding space; to provide a neat, rugged," efcient and economical construction, and in general, to provide an improved arrangement of the character specified.

In the drawings which illustrate my invention as applied to the primary of an induction coil or transformer,

Fig. 1 is a perspective view of the completed primary coil unit.

Fig. 2 is a sectional elevation showing the various parts of the mold separated from each other to illustrate the mechanical construction.

Fig. 3 is a sectional elevation of the mold containing the finished spool or bobbin ready to be removed therefrom.

Fig. 4 is a perspective view of the bobbin molded on the core after removal from the mold shown in Fig. 3. Y

Fig. 5 is an axial section of the core -bobbin and primary winding thereon.

Fig. 6 is a section taken on the line 6-6 of' Fig. 5.

Fig. 7 is a plan View of a portion of Fig. 5, and y Fig. 8 is a sectional elevation showing the mold with the completed primary coil contained therein after the final molding operation and ready to be removed from the mold.

Referring to the drawings, it will be seen that in the present instance the core 10 is composed of a'bundle of round wires 11 of Norway iron or other suitable highly magnetic material. In order to mold the lsame in a compact bundle and for another purpose which will hereinafter appear, the bundle of wires, all cut tothe same length, isv enclosed or wrapped with a sheet of fabric 12, pref- 1928. Serial N0. 287,305.

erably stout woven linen or cotton cloth, which is impregnated with a solution of bakelie varnish or analogous material capable of being hardened by the use of heat and pressure.

The .mold or dies for preforming the rst molding operation comprise a pair of heads- 13 and 14, having at their opposed inner faces a pair of recesses as at 15 of suitable diameter to fit snugly over the ends of the core 10. The heads 13 and 14 are of such thickness that when they are clamped together with the ends of the core 10 seated in the recesses 15, the outer faces of the heads 13 and 14 are the right distance apart to iit snugly between the inner faces 16 of the ends of a rectangular aperture 17 formed in a rectangular block 18. In order to facilitate assembly of the core in the recesses 15 of the heads, said recesses are flared at their outer ends as well shown in Fig. 3. As shown best in Fig. 3, the heads 13 and 14 are of the same vertical height as the Vertical thickness of the apertured block 18.

After the core 10 and heads 13 and 14 have been assembled and inserted in the aperture of the block 18, the assembly of the upper and lower parts of the mold is completed asgether with a parting line midway of the i' mold structure, are of suitable length to lit snugly between the inner surfaces vof the heads 13 and 14 of the mold.

The counterbores in the parts'20 and25 which provide space for thematerial of the anges of the bobbin are formed with inwardly projectinor circumferentially extending beads 26 of substantially semicircular cross-section so that in molding the spool or bobbin there are formed in the outer surfaces of the'edges of said flanges, small grooves as indicated at 27 in Fig. 4. These grooves are provided for a purpose which will hereinafter appear.

In order to facilitate the leadin out of the conductors from the winding whlch is to be subsequently applied to the spool or bobbin, small notches are provided in the flanges or, in the present instance, one of the flanges of the bobbin. The outer terminal of the winding will be accommodated in a shallow slot or notch 28 at the upper edge of the flange 29. while the inner terminal is accommodated in an L-shaped notch 30. Said notches 28 and 30 are formed respectively by small pieces 31 and 32 inserted in thecounterbore at one end of the mold.

The molding operation is eected in a wellknown manner. Preferably, a supply of the plastic material in powdered form is placed in the recesses above the core before the upper half of the mold has been applied and while there is still a small space between the plate 19 of the lower half of the mold and the lower faces or edges of the core supportingv elements.

As the parts of the mold have been heated from a previous operation, the material commences' to liquefy or become plastic very quickly and after the upper half of the mold has been applied the mold as a whole is sub- ]ected to gradually increasing pressure S0 that by the time the material is completely hquefied or plasticized the parts have reached the position shown in Fig. 3 of the drawings with the plastic material completely filling all the interstices of the mold cavity. As an incident to the molding operation, the material with which the core wrapping 12 is impregnated also becomes hardened and intimately incorporated with the outer surface of the bundle of wires comprising the core and l it also becomes autogenously united with the sleeve or shell 33 of the bobbin. After the molding operation has been completed, the

mold is opened in an obvious manner and the completed core and bobbin unit as shown in Fig. 4 is readyfor the winding operation.

Before starting the applicatmn of the winding 34, the end of the latter is brought out at the end of the spool. Although this may be accomplished in various ways, I have lllustrated in the present instance a leading in wire 35 formed of tubular braided copper wire fiattened as best shown by comparison of Figs. 5 and 7. The inner end of said lead conductor 35 is connected to the end of the coil winding by slipping the bared end of the latter into the expanded end of the lead conductor 35 and preferablysoldered.` It will be understood that tape or other suitable inf sulating material is applied to the splices so as to prevent improper contact with portions of the winding. v f l It will be observed that the braided conductor 35 is suitably bent so as to fit .within other the L-shaped slot or notch 30 formed in the flange 29 of the spool as previously described. 1 After the inner lead wire has been connected to the end of the winding and suitably insulated, the winding is completed in the customarymanner and it may be observed here that it is not necessary to provide any other insulating material to prevent improper electrical contacts nor is it necessary to provide any further support for the turns of the winding. This is due to the fact that the heads or flanges of the bobbin are integrally united to the ends of the sleeve or shell 33 which itself is thoroughly incorporated with or united to the outer surface of the core structure. After the required number of layers or turns has been applied, the outer end of the winding is connected to the other leading in wire 36 as in the case of the inner leading in wire 35, the conductor 36 being laid in the notch 28 of fiange 29. In order to anchor properly the end of the leading in wire 3G,`the insulating tape 37 is preferably inserted under the last few turns of the winding which thus hold the end of the terminal wire rigidly in proper position.

After the winding has been completed in the form shown in Figs. 5, 6, and 7 the structure is inserted in the finishing mold shown in F ig. 8, the parts of this mold being constructed in substantially the same manner as in the case of the first step shown in Fig. 3. However, in the finishing mold, provision is made for bringing out the leading in wires from the right hand head 38 of the mold cavity. This is effected by forming apertures 39 and 40 extending in a direction parallel with the axis, the wires 35 and 36 being threaded through said apertures 39 and 40 as an incident to the assembly of the head 38 on the end of the bobbin. Also, the end wall of the rectangular apertured portion 41 of the nishing mold structure is notched out as shown at 42 and 43 to accommodate the 'ends of said leadingv in wires. i

The heads 38 and 44 are suitably recessed on their inner faces to fit the outer ends of the composite structure and the inner faces of the upper and lower mold parts 45 and 46 are suitably shaped to form a mold for the shell on the outside of the winding 34. The second molding operation does not materially differ from the procedure outlined in describing the first step of the molding process.

After the completion of the second molding operation the outer shell or jacket 47 willbe found to be intimately united to the outer edges of the heads or fianges 29 of the spool. An improved result is obtained if` the grooves and fianges of the bobbin, before insertion in the mold, are coated with bakelite varnish or cement, thereby insuring perfect union between the new material and that previously molded. Efficiency of such union is further increased by reason of the fact that the material of the second molding operation interlocks in the grooves 27 of the flanges and also by shrinkage of the outer` shell 33.

The completed coil structure as shown in Fig l of the drawings will be found to be thoroughly sealed, permanently'waterproof. The winding has a high copper efficiency because the inner shell 33 can be of comparatively slight thickness and the flanges of the spool are rigidly enough united to said shell 33 to require no further reinforcing which might result in loss of valuable winding space. The shell 33' maybe made relatively thin as compared with the thickness of a separately molded bobbin by reason of the fact that the shell and the bundle of core wires each contribute to support each other mutually. In this connection, it may be observed that part of the plastic material penetrates the outer layer or layers of the bundle of core wires, thus cementing the same rigidly together and in effect, increasing the effective thickness and strength of the core shell.

Furthermore, by reason of the very heavy pressure incident to the first molding operation, the bundle of core wires is very highly compressed, in fact-the pressure is so great that the wires will be found to have arranged themselves in a honeycomb or geometric pattern of minimum area so that loss of eliiciency due to unnecessary air space in the core is reduced to a minimum. Also, by reason of such heavy pressure the wires of the core are so clamped together that thereafter there can be no looseness or rattling cf the individual wires. This is an important consideration where the core is to be used in connection With an armature or in a location where it is subject to excessive vibration. Where the coil is-,to be used in connection Ywith a secondary winding or must be inserted into a space'of predetermined size, this construc-wl tion is highly advantageous in view of the fact that the Isurface of the coil structure is cylindrical, of accurate size and free from objectionable exterior projecting portions.

The described details of manipulation and construction being illustrative of only one application of my invention, the scope of same shell and spaced apart to provide a space for an electrical winding to be wound thereon.

3. In combination, a magnetic core, a sleeve of insulating material molded around and united with the outer surface of said core and provided at each end with an integral outwardly projecting circumferential flange, a winding on said sleeve and an outer sheath of insulating material molded around the winding and integrally united to the circumference of said flanges to form a weatherproof casing for said winding.

4. In combination, a bundle of magnetic wires forming a magnetic core and a sleeve of insulating material molded around and incorporated with the outer surface of said core, circumferential outwardly projecting flanges being provided on the ends of said sleeve to form a coil winding space between said flanges, the material of said sleeve and -flanges possessing sufficient strength and 'rigidity to maintain said bundle of wires in intimate contact and in substantially geometric relation. j y

5. In combination, a rigid bobbin comprising a tube with integral outwardly projecting end flanges, an electric Winding in the space between said flanges, and a shell of rigid material molded around said winding and united to said flanges so as to provide a hermeticallysealed casing completely enclosing said winding.

6. The improvement in the method of providing a bobbin to receive an electrical winding for energizing a magnetic core composed of a bundle of wires which consists in supporting the bundle of wire at its ends in a f mold cavity, and, while so supported, molding a rigid bobbin around said bundle by subjecting moldable material insaid cavity to heat and pressure, said pressure serving to compress the bundle of wires and to in-v corporate the outer layer of said wires with the material of the bobbin.

June 18, 1928.

j I-IGrO I-I. WERMINE.

should be determined by reference to the appended claims, said claims being construed as broadly as possible, consistent with the state of the art.

I claim as my invention: l. In combination, a bundle of wires of 'magnetic material and an envelope of insulat- 

